Statistical design for optimization of process parameters for biodecolorization of reactive orange 4 azo dye by Bacillus cereus isolate

Abstract

In the present study, different approaches are being compared for the decolorization of reactive orange 4 monoazo dye by Bacillus cereus isolate under varied cultural and nutritional conditions. By employing conventional one-factor-at-a-time approach, the bacterial strain exhibited decolorization activity over a wide range of pH (7.0-9.0), temperature (30-38°C), dye concentration (50-200 mg L-1 MSM) and inoculum size (1.0-6.0%, v/v), with peak activity (68.2% color removal) at pH 8.0, 35°C, 50 mg dye L-1 MSM and 4.0% (v/v) inoculum in the presence of 1.0% (w/v) glucose as carbon/energy source and 0.2% (w/v) ammonium nitrate within 72 h incubation. Under response surface methodology (RSM using Box-Behnken design) approach, the dye decolorization enhanced to 100% at optimized 40 mg reactive orange L-1 MSM, glucose 1.0% (w/v) and ammonium nitrate 0.2% (w/v) during 72 h of incubation. The dye decolorization time was advanced by 12 h in bioreactor trial and 100% color removal was achieved within only 60 h incubation. In future experimentation, we envisage to test the potential of our isolate for the decolorization of other variety of azo dyes, mixture of dyes as well as the real textile effluent.